Lasers are commonly used in many modern components. One use that has recently become more common is the use of lasers in data networks. Lasers are used in many fiber optic communication systems to transmit digital data on a network. In one exemplary configuration, a laser may be modulated by digital data to produce an optical signal, including periods of light and dark output that represents a binary data stream. In actual practice, the lasers output a high optical output representing binary highs and a lower power optical output representing binary lows. To obtain quick reaction time, the laser is constantly on, but varies from a high optical output to a lower optical output.
Optical networks have various advantages over other types of networks such as copper wire based networks. For example, many existing copper wire networks operate at near maximum possible data transmission rates and at near maximum possible distances for copper wire technology. On the other hand, many existing optical networks exceed, both in data transmission rate and distance, the maximums that are possible for copper wire networks. That is, optical networks are able to reliably transmit data at higher rates over further distances than is possible with copper wire networks.
Lasers typically have an optimal operating temperature range, which is typically around room temperature. For optimal performance of the laser, the laser temperature needs to be controlled to some range. Operation outside of the temperature range can reduce the laser's performance to the point it is unusable. For example, a decrease in performance of the laser's turn-on time, turn-off time, optical modal properties and optical power may be experienced. For semiconductor lasers such as a VCSELs, DFB lasers, or EMLs, the lasing mode is typically locked by the laser feedback system, which may include, for example, DBR mirrors, or gratings. The gain, i.e., the amplification of the light, is provided by the laser active region. Generally at cold temperatures, the laser active region wavelength shifts to a shorter side, also known as a blue shift, due to semiconductor material properties. Therefore at cold temperatures, the gain region peak wavelength may be significantly shorter than the lasing wavelength. This may give rise to a host of problems for laser operation.
Illustratively, operation at colder temperatures may cause the laser's reaction speed, the speed at which the laser changes from high power output to low power output, to be decreased, thus lengthening the laser's reaction time and reducing the communication bandwidth. Cold temperatures may also cause a laser intended to operate in a single mode fashion to operate in a multi-mode fashion. Cold operating temperatures may also reduce the amount of power that a laser can output. Despite these limitations at these temperatures, there is increased demand for laser modules that operate in wider temperature ranges and at colder and hotter temperatures.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.